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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2010 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.base;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>import com.google.common.annotations.GwtCompatible;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.annotations.VisibleForTesting;<a name="line.23"></a>
<span class="sourceLineNo">024</span><a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.Formatter;<a name="line.25"></a>
<span class="sourceLineNo">026</span><a name="line.26"></a>
<span class="sourceLineNo">027</span>import javax.annotation.Nullable;<a name="line.27"></a>
<span class="sourceLineNo">028</span><a name="line.28"></a>
<span class="sourceLineNo">029</span>/**<a name="line.29"></a>
<span class="sourceLineNo">030</span> * Static utility methods pertaining to {@code String} or {@code CharSequence}<a name="line.30"></a>
<span class="sourceLineNo">031</span> * instances.<a name="line.31"></a>
<span class="sourceLineNo">032</span> *<a name="line.32"></a>
<span class="sourceLineNo">033</span> * @author Kevin Bourrillion<a name="line.33"></a>
<span class="sourceLineNo">034</span> * @since 3.0<a name="line.34"></a>
<span class="sourceLineNo">035</span> */<a name="line.35"></a>
<span class="sourceLineNo">036</span>@GwtCompatible<a name="line.36"></a>
<span class="sourceLineNo">037</span>public final class Strings {<a name="line.37"></a>
<span class="sourceLineNo">038</span>  private Strings() {}<a name="line.38"></a>
<span class="sourceLineNo">039</span><a name="line.39"></a>
<span class="sourceLineNo">040</span>  /**<a name="line.40"></a>
<span class="sourceLineNo">041</span>   * Returns the given string if it is non-null; the empty string otherwise.<a name="line.41"></a>
<span class="sourceLineNo">042</span>   *<a name="line.42"></a>
<span class="sourceLineNo">043</span>   * @param string the string to test and possibly return<a name="line.43"></a>
<span class="sourceLineNo">044</span>   * @return {@code string} itself if it is non-null; {@code ""} if it is null<a name="line.44"></a>
<span class="sourceLineNo">045</span>   */<a name="line.45"></a>
<span class="sourceLineNo">046</span>  public static String nullToEmpty(@Nullable String string) {<a name="line.46"></a>
<span class="sourceLineNo">047</span>    return (string == null) ? "" : string;<a name="line.47"></a>
<span class="sourceLineNo">048</span>  }<a name="line.48"></a>
<span class="sourceLineNo">049</span><a name="line.49"></a>
<span class="sourceLineNo">050</span>  /**<a name="line.50"></a>
<span class="sourceLineNo">051</span>   * Returns the given string if it is nonempty; {@code null} otherwise.<a name="line.51"></a>
<span class="sourceLineNo">052</span>   *<a name="line.52"></a>
<span class="sourceLineNo">053</span>   * @param string the string to test and possibly return<a name="line.53"></a>
<span class="sourceLineNo">054</span>   * @return {@code string} itself if it is nonempty; {@code null} if it is<a name="line.54"></a>
<span class="sourceLineNo">055</span>   *     empty or null<a name="line.55"></a>
<span class="sourceLineNo">056</span>   */<a name="line.56"></a>
<span class="sourceLineNo">057</span>  public static @Nullable String emptyToNull(@Nullable String string) {<a name="line.57"></a>
<span class="sourceLineNo">058</span>    return isNullOrEmpty(string) ? null : string;<a name="line.58"></a>
<span class="sourceLineNo">059</span>  }<a name="line.59"></a>
<span class="sourceLineNo">060</span><a name="line.60"></a>
<span class="sourceLineNo">061</span>  /**<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * Returns {@code true} if the given string is null or is the empty string.<a name="line.62"></a>
<span class="sourceLineNo">063</span>   *<a name="line.63"></a>
<span class="sourceLineNo">064</span>   * &lt;p&gt;Consider normalizing your string references with {@link #nullToEmpty}.<a name="line.64"></a>
<span class="sourceLineNo">065</span>   * If you do, you can use {@link String#isEmpty()} instead of this<a name="line.65"></a>
<span class="sourceLineNo">066</span>   * method, and you won't need special null-safe forms of methods like {@link<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * String#toUpperCase} either. Or, if you'd like to normalize "in the other<a name="line.67"></a>
<span class="sourceLineNo">068</span>   * direction," converting empty strings to {@code null}, you can use {@link<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * #emptyToNull}.<a name="line.69"></a>
<span class="sourceLineNo">070</span>   *<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * @param string a string reference to check<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * @return {@code true} if the string is null or is the empty string<a name="line.72"></a>
<span class="sourceLineNo">073</span>   */<a name="line.73"></a>
<span class="sourceLineNo">074</span>  public static boolean isNullOrEmpty(@Nullable String string) {<a name="line.74"></a>
<span class="sourceLineNo">075</span>    return string == null || string.length() == 0; // string.isEmpty() in Java 6<a name="line.75"></a>
<span class="sourceLineNo">076</span>  }<a name="line.76"></a>
<span class="sourceLineNo">077</span><a name="line.77"></a>
<span class="sourceLineNo">078</span>  /**<a name="line.78"></a>
<span class="sourceLineNo">079</span>   * Returns a string, of length at least {@code minLength}, consisting of<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * {@code string} prepended with as many copies of {@code padChar} as are<a name="line.80"></a>
<span class="sourceLineNo">081</span>   * necessary to reach that length. For example,<a name="line.81"></a>
<span class="sourceLineNo">082</span>   *<a name="line.82"></a>
<span class="sourceLineNo">083</span>   * &lt;ul&gt;<a name="line.83"></a>
<span class="sourceLineNo">084</span>   * &lt;li&gt;{@code padStart("7", 3, '0')} returns {@code "007"}<a name="line.84"></a>
<span class="sourceLineNo">085</span>   * &lt;li&gt;{@code padStart("2010", 3, '0')} returns {@code "2010"}<a name="line.85"></a>
<span class="sourceLineNo">086</span>   * &lt;/ul&gt;<a name="line.86"></a>
<span class="sourceLineNo">087</span>   *<a name="line.87"></a>
<span class="sourceLineNo">088</span>   * &lt;p&gt;See {@link Formatter} for a richer set of formatting capabilities.<a name="line.88"></a>
<span class="sourceLineNo">089</span>   *<a name="line.89"></a>
<span class="sourceLineNo">090</span>   * @param string the string which should appear at the end of the result<a name="line.90"></a>
<span class="sourceLineNo">091</span>   * @param minLength the minimum length the resulting string must have. Can be<a name="line.91"></a>
<span class="sourceLineNo">092</span>   *     zero or negative, in which case the input string is always returned.<a name="line.92"></a>
<span class="sourceLineNo">093</span>   * @param padChar the character to insert at the beginning of the result until<a name="line.93"></a>
<span class="sourceLineNo">094</span>   *     the minimum length is reached<a name="line.94"></a>
<span class="sourceLineNo">095</span>   * @return the padded string<a name="line.95"></a>
<span class="sourceLineNo">096</span>   */<a name="line.96"></a>
<span class="sourceLineNo">097</span>  public static String padStart(String string, int minLength, char padChar) {<a name="line.97"></a>
<span class="sourceLineNo">098</span>    checkNotNull(string);  // eager for GWT.<a name="line.98"></a>
<span class="sourceLineNo">099</span>    if (string.length() &gt;= minLength) {<a name="line.99"></a>
<span class="sourceLineNo">100</span>      return string;<a name="line.100"></a>
<span class="sourceLineNo">101</span>    }<a name="line.101"></a>
<span class="sourceLineNo">102</span>    StringBuilder sb = new StringBuilder(minLength);<a name="line.102"></a>
<span class="sourceLineNo">103</span>    for (int i = string.length(); i &lt; minLength; i++) {<a name="line.103"></a>
<span class="sourceLineNo">104</span>      sb.append(padChar);<a name="line.104"></a>
<span class="sourceLineNo">105</span>    }<a name="line.105"></a>
<span class="sourceLineNo">106</span>    sb.append(string);<a name="line.106"></a>
<span class="sourceLineNo">107</span>    return sb.toString();<a name="line.107"></a>
<span class="sourceLineNo">108</span>  }<a name="line.108"></a>
<span class="sourceLineNo">109</span><a name="line.109"></a>
<span class="sourceLineNo">110</span>  /**<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * Returns a string, of length at least {@code minLength}, consisting of<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * {@code string} appended with as many copies of {@code padChar} as are<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * necessary to reach that length. For example,<a name="line.113"></a>
<span class="sourceLineNo">114</span>   *<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * &lt;ul&gt;<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * &lt;li&gt;{@code padEnd("4.", 5, '0')} returns {@code "4.000"}<a name="line.116"></a>
<span class="sourceLineNo">117</span>   * &lt;li&gt;{@code padEnd("2010", 3, '!')} returns {@code "2010"}<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * &lt;/ul&gt;<a name="line.118"></a>
<span class="sourceLineNo">119</span>   *<a name="line.119"></a>
<span class="sourceLineNo">120</span>   * &lt;p&gt;See {@link Formatter} for a richer set of formatting capabilities.<a name="line.120"></a>
<span class="sourceLineNo">121</span>   *<a name="line.121"></a>
<span class="sourceLineNo">122</span>   * @param string the string which should appear at the beginning of the result<a name="line.122"></a>
<span class="sourceLineNo">123</span>   * @param minLength the minimum length the resulting string must have. Can be<a name="line.123"></a>
<span class="sourceLineNo">124</span>   *     zero or negative, in which case the input string is always returned.<a name="line.124"></a>
<span class="sourceLineNo">125</span>   * @param padChar the character to append to the end of the result until the<a name="line.125"></a>
<span class="sourceLineNo">126</span>   *     minimum length is reached<a name="line.126"></a>
<span class="sourceLineNo">127</span>   * @return the padded string<a name="line.127"></a>
<span class="sourceLineNo">128</span>   */<a name="line.128"></a>
<span class="sourceLineNo">129</span>  public static String padEnd(String string, int minLength, char padChar) {<a name="line.129"></a>
<span class="sourceLineNo">130</span>    checkNotNull(string);  // eager for GWT.<a name="line.130"></a>
<span class="sourceLineNo">131</span>    if (string.length() &gt;= minLength) {<a name="line.131"></a>
<span class="sourceLineNo">132</span>      return string;<a name="line.132"></a>
<span class="sourceLineNo">133</span>    }<a name="line.133"></a>
<span class="sourceLineNo">134</span>    StringBuilder sb = new StringBuilder(minLength);<a name="line.134"></a>
<span class="sourceLineNo">135</span>    sb.append(string);<a name="line.135"></a>
<span class="sourceLineNo">136</span>    for (int i = string.length(); i &lt; minLength; i++) {<a name="line.136"></a>
<span class="sourceLineNo">137</span>      sb.append(padChar);<a name="line.137"></a>
<span class="sourceLineNo">138</span>    }<a name="line.138"></a>
<span class="sourceLineNo">139</span>    return sb.toString();<a name="line.139"></a>
<span class="sourceLineNo">140</span>  }<a name="line.140"></a>
<span class="sourceLineNo">141</span><a name="line.141"></a>
<span class="sourceLineNo">142</span>  /**<a name="line.142"></a>
<span class="sourceLineNo">143</span>   * Returns a string consisting of a specific number of concatenated copies of<a name="line.143"></a>
<span class="sourceLineNo">144</span>   * an input string. For example, {@code repeat("hey", 3)} returns the string<a name="line.144"></a>
<span class="sourceLineNo">145</span>   * {@code "heyheyhey"}.<a name="line.145"></a>
<span class="sourceLineNo">146</span>   *<a name="line.146"></a>
<span class="sourceLineNo">147</span>   * @param string any non-null string<a name="line.147"></a>
<span class="sourceLineNo">148</span>   * @param count the number of times to repeat it; a nonnegative integer<a name="line.148"></a>
<span class="sourceLineNo">149</span>   * @return a string containing {@code string} repeated {@code count} times<a name="line.149"></a>
<span class="sourceLineNo">150</span>   *     (the empty string if {@code count} is zero)<a name="line.150"></a>
<span class="sourceLineNo">151</span>   * @throws IllegalArgumentException if {@code count} is negative<a name="line.151"></a>
<span class="sourceLineNo">152</span>   */<a name="line.152"></a>
<span class="sourceLineNo">153</span>  public static String repeat(String string, int count) {<a name="line.153"></a>
<span class="sourceLineNo">154</span>    checkNotNull(string);  // eager for GWT.<a name="line.154"></a>
<span class="sourceLineNo">155</span><a name="line.155"></a>
<span class="sourceLineNo">156</span>    if (count &lt;= 1) {<a name="line.156"></a>
<span class="sourceLineNo">157</span>      checkArgument(count &gt;= 0, "invalid count: %s", count);<a name="line.157"></a>
<span class="sourceLineNo">158</span>      return (count == 0) ? "" : string;<a name="line.158"></a>
<span class="sourceLineNo">159</span>    }<a name="line.159"></a>
<span class="sourceLineNo">160</span><a name="line.160"></a>
<span class="sourceLineNo">161</span>    // IF YOU MODIFY THE CODE HERE, you must update StringsRepeatBenchmark<a name="line.161"></a>
<span class="sourceLineNo">162</span>    final int len = string.length();<a name="line.162"></a>
<span class="sourceLineNo">163</span>    final long longSize = (long) len * (long) count;<a name="line.163"></a>
<span class="sourceLineNo">164</span>    final int size = (int) longSize;<a name="line.164"></a>
<span class="sourceLineNo">165</span>    if (size != longSize) {<a name="line.165"></a>
<span class="sourceLineNo">166</span>      throw new ArrayIndexOutOfBoundsException("Required array size too large: "<a name="line.166"></a>
<span class="sourceLineNo">167</span>          + String.valueOf(longSize));<a name="line.167"></a>
<span class="sourceLineNo">168</span>    }<a name="line.168"></a>
<span class="sourceLineNo">169</span><a name="line.169"></a>
<span class="sourceLineNo">170</span>    final char[] array = new char[size];<a name="line.170"></a>
<span class="sourceLineNo">171</span>    string.getChars(0, len, array, 0);<a name="line.171"></a>
<span class="sourceLineNo">172</span>    int n;<a name="line.172"></a>
<span class="sourceLineNo">173</span>    for (n = len; n &lt; size - n; n &lt;&lt;= 1) {<a name="line.173"></a>
<span class="sourceLineNo">174</span>      System.arraycopy(array, 0, array, n, n);<a name="line.174"></a>
<span class="sourceLineNo">175</span>    }<a name="line.175"></a>
<span class="sourceLineNo">176</span>    System.arraycopy(array, 0, array, n, size - n);<a name="line.176"></a>
<span class="sourceLineNo">177</span>    return new String(array);<a name="line.177"></a>
<span class="sourceLineNo">178</span>  }<a name="line.178"></a>
<span class="sourceLineNo">179</span><a name="line.179"></a>
<span class="sourceLineNo">180</span>  /**<a name="line.180"></a>
<span class="sourceLineNo">181</span>   * Returns the longest string {@code prefix} such that<a name="line.181"></a>
<span class="sourceLineNo">182</span>   * {@code a.toString().startsWith(prefix) &amp;&amp; b.toString().startsWith(prefix)},<a name="line.182"></a>
<span class="sourceLineNo">183</span>   * taking care not to split surrogate pairs. If {@code a} and {@code b} have<a name="line.183"></a>
<span class="sourceLineNo">184</span>   * no common prefix, returns the empty string.<a name="line.184"></a>
<span class="sourceLineNo">185</span>   *<a name="line.185"></a>
<span class="sourceLineNo">186</span>   * @since 11.0<a name="line.186"></a>
<span class="sourceLineNo">187</span>   */<a name="line.187"></a>
<span class="sourceLineNo">188</span>  public static String commonPrefix(CharSequence a, CharSequence b) {<a name="line.188"></a>
<span class="sourceLineNo">189</span>    checkNotNull(a);<a name="line.189"></a>
<span class="sourceLineNo">190</span>    checkNotNull(b);<a name="line.190"></a>
<span class="sourceLineNo">191</span><a name="line.191"></a>
<span class="sourceLineNo">192</span>    int maxPrefixLength = Math.min(a.length(), b.length());<a name="line.192"></a>
<span class="sourceLineNo">193</span>    int p = 0;<a name="line.193"></a>
<span class="sourceLineNo">194</span>    while (p &lt; maxPrefixLength &amp;&amp; a.charAt(p) == b.charAt(p)) {<a name="line.194"></a>
<span class="sourceLineNo">195</span>      p++;<a name="line.195"></a>
<span class="sourceLineNo">196</span>    }<a name="line.196"></a>
<span class="sourceLineNo">197</span>    if (validSurrogatePairAt(a, p - 1) || validSurrogatePairAt(b, p - 1)) {<a name="line.197"></a>
<span class="sourceLineNo">198</span>      p--;<a name="line.198"></a>
<span class="sourceLineNo">199</span>    }<a name="line.199"></a>
<span class="sourceLineNo">200</span>    return a.subSequence(0, p).toString();<a name="line.200"></a>
<span class="sourceLineNo">201</span>  }<a name="line.201"></a>
<span class="sourceLineNo">202</span><a name="line.202"></a>
<span class="sourceLineNo">203</span>  /**<a name="line.203"></a>
<span class="sourceLineNo">204</span>   * Returns the longest string {@code suffix} such that<a name="line.204"></a>
<span class="sourceLineNo">205</span>   * {@code a.toString().endsWith(suffix) &amp;&amp; b.toString().endsWith(suffix)},<a name="line.205"></a>
<span class="sourceLineNo">206</span>   * taking care not to split surrogate pairs. If {@code a} and {@code b} have<a name="line.206"></a>
<span class="sourceLineNo">207</span>   * no common suffix, returns the empty string.<a name="line.207"></a>
<span class="sourceLineNo">208</span>   *<a name="line.208"></a>
<span class="sourceLineNo">209</span>   * @since 11.0<a name="line.209"></a>
<span class="sourceLineNo">210</span>   */<a name="line.210"></a>
<span class="sourceLineNo">211</span>  public static String commonSuffix(CharSequence a, CharSequence b) {<a name="line.211"></a>
<span class="sourceLineNo">212</span>    checkNotNull(a);<a name="line.212"></a>
<span class="sourceLineNo">213</span>    checkNotNull(b);<a name="line.213"></a>
<span class="sourceLineNo">214</span><a name="line.214"></a>
<span class="sourceLineNo">215</span>    int maxSuffixLength = Math.min(a.length(), b.length());<a name="line.215"></a>
<span class="sourceLineNo">216</span>    int s = 0;<a name="line.216"></a>
<span class="sourceLineNo">217</span>    while (s &lt; maxSuffixLength<a name="line.217"></a>
<span class="sourceLineNo">218</span>        &amp;&amp; a.charAt(a.length() - s - 1) == b.charAt(b.length() - s - 1)) {<a name="line.218"></a>
<span class="sourceLineNo">219</span>      s++;<a name="line.219"></a>
<span class="sourceLineNo">220</span>    }<a name="line.220"></a>
<span class="sourceLineNo">221</span>    if (validSurrogatePairAt(a, a.length() - s - 1)<a name="line.221"></a>
<span class="sourceLineNo">222</span>        || validSurrogatePairAt(b, b.length() - s - 1)) {<a name="line.222"></a>
<span class="sourceLineNo">223</span>      s--;<a name="line.223"></a>
<span class="sourceLineNo">224</span>    }<a name="line.224"></a>
<span class="sourceLineNo">225</span>    return a.subSequence(a.length() - s, a.length()).toString();<a name="line.225"></a>
<span class="sourceLineNo">226</span>  }<a name="line.226"></a>
<span class="sourceLineNo">227</span><a name="line.227"></a>
<span class="sourceLineNo">228</span>  /**<a name="line.228"></a>
<span class="sourceLineNo">229</span>   * True when a valid surrogate pair starts at the given {@code index} in the<a name="line.229"></a>
<span class="sourceLineNo">230</span>   * given {@code string}. Out-of-range indexes return false.<a name="line.230"></a>
<span class="sourceLineNo">231</span>   */<a name="line.231"></a>
<span class="sourceLineNo">232</span>  @VisibleForTesting<a name="line.232"></a>
<span class="sourceLineNo">233</span>  static boolean validSurrogatePairAt(CharSequence string, int index) {<a name="line.233"></a>
<span class="sourceLineNo">234</span>    return index &gt;= 0 &amp;&amp; index &lt;= (string.length() - 2)<a name="line.234"></a>
<span class="sourceLineNo">235</span>        &amp;&amp; Character.isHighSurrogate(string.charAt(index))<a name="line.235"></a>
<span class="sourceLineNo">236</span>        &amp;&amp; Character.isLowSurrogate(string.charAt(index + 1));<a name="line.236"></a>
<span class="sourceLineNo">237</span>  }<a name="line.237"></a>
<span class="sourceLineNo">238</span>}<a name="line.238"></a>




























































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